Co-authors: Deborah L. Sulsky (University of New Mexico), Howard L. Schreyer (University of New Mexico) When leads in sea ice expose warm underlying ocean to the frigid winter atmosphere, new ice is formed rapidly by freezing ocean water. Then convergence or closing of the pack ice forces the new ice in leads to pile up into ridges and to be forced down into keels. Together with thermodynamic growth, these mechanical processes shape the thickness distribution of the ice cover, and impact the overall strength of pack ice. Specifically, the deformation and strength of ice are not isotropic but vary with the thickness and orientation of the categories. To reflect these facts, we develop an anisotropic constitutive model for sea ice consisting an oriented thickness distribution. The model describes anisotropically mechanical responses in both elastic and failure regimes. In the elastic regime, the constitutive relation implicitly reflects the strong and weak directions of the pack ice depending on the distribution of thin ice and thicker ice. The existence of open water, a special case of thin ice, is also reflected in the elastic constitutive relation in which the free-traction condition is satisfied. In the failure regime, the model predicts when an initial failure, i.e. a microcrack, occurs and what the direction of the failure is. The evolution of a microcrack to a macrocrack, i.e. when free-traction crack surfaces are completely formed, is also modeled, and a numerical procedure is proposed to determine the width of cracks. Sample paths in stress space are used to illustrate how the model can simulate failure. Several examples of failure surfaces are presented to describe the behavior of ice when varying thickness distributions. The model predictions are also illustrated and compared with previous modeling efforts by examining regions under idealized loading.

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